1. Field of the Invention
The present invention relates to an ultrasonic probe, and more particularly to a variable type ultrasonic probe capable of changing over the focus from one to the other in a depth direction by separate arrangement of piezoelectric elements in a widthwise direction.
2. Description of the Related Art
An ultrasonic probe is used in, for example, ultrasonic diagnostic equipment for medical care purpose, as an ultrasonic transducer, which transmits and receives an ultrasonic wave, for acquiring information of a living organism from the disease portions. There are various kinds of ultrasonic probes depending on functions and shapes of the probes, and as one of them, there is an ultrasonic probe capable of changing over the focus thereof in a depth direction from the surface of a living body, i.e., a tested body. This type of an ultrasonic probe is called a variable type probe.
FIG. 1 illustrates the constitution of a conventional variable type probe in which a plurality of piezoelectric units 1 is arrayed in a line on backing member 2. Each piezoelectric unit 1 is provided with a piezoelectric member, and excitation electrodes provided on the upper and lower faces of the piezoelectric member, respectively. Further, piezoelectric unit 1 is separated into three pieces, namely, piezoelectric elements 1a, 1b and 1c, in the widthwise direction.
The variable type probe is manufactured by the method described hereinbelow:
For example, flexible printed boards 3a, 3b, and 3c, which are used for externally conducting the excitation electrodes, are attached to the center and opposite sides of the bottom face of a plate-like member of piezoelectric body, and then inpouring or filling of resin is performed so as to form backing member 2. Subsequently, cuttings reaching from the piezoelectric plate-like member to backing member 2 are applied so as to sever the piezoelectric plate member in a lengthwise direction to thereby obtain a plurality of separate piezoelectric units 1. Then, the piezoelectric plate-like member is severed in a widthwise direction, so that each piezoelectric unit 1 is separate into three piezoelectric elements 1a, 1b and 1c, i.e., one central and two side-arranged elements. The lower face electrodes of piezoelectric elements 1a, 1b and 1c are led by flexible printed board 3a, 3b and 3c, respectively. Although upper face electrodes of piezoelectric elements 1a, 1b and 1c are not shown in FIG. 1, these upper face electrodes of piezoelectric elements 1a, 1b and 1c are electrically connected to and grounded by common electrode (not shown) which is arranged to cover the plurality of piezoelectric units 1.
In the described variable type ultrasonic probe, either three piezoelectric elements 1a, 1b and 1c separated widthwise are commonly driven or only the central piezoelectric element 1b is driven to thereby change over the focus from the surface of a living body from one to the other focal point. When the three piezoelectric elements 1a, 1b and 1c are simultaneously driven, the focal distance becomes long. On the other hand, when only the central piezoelectric element 1b is driven, the focal distance becomes short.
At this stage, in the ultrasonic probe, there are different types such as, for example, a convex type probe and a linear type probe, depending on how a plurality of piezoelectric elements are arranged in respective probes. In the convex type probe, as shown in FIG. 2, a plurality of piezoelectric elements 1 are arrayed to be directed outward along an arcuate line, and is therefore suitable for arcuately emitting ultrasonic wave so as to detect ultrasonic echo within a predetermined angular range. On the other hand, in the linear type probe, a plurality of piezoelectric elements 1 is arrayed in a straight line to be oriented in the same direction. The linear type probe is used for emitting ultrasonic wave in only a specified direction.
Backing member 2 of the variable probe shown in FIG. 1 has an approximately planar face without any curve, and piezoelectric units 1 are arrayed on such backing member 2. Thus, the variable type probe of FIG. 1 can be classified in the linear type probe.
In the variable type probe of FIG. 1, flexible printed board 3b is connected to central piezoelectric element 1b, which is one of three piezoelectric elements 1a, 1b, and 1c constituting piezoelectric element 1, so as to depend vertically as shown in FIG. 1 to thereby permit the lower face electrode to be led. Therefore, when the surface of backing member 2 is arcuately curved as shown in FIG. 2 while permitting a plurality of piezoelectric units 1 are arrayed thereon, flexible printed board 3b depending from the central piezoelectric elements 1b of respective piezoelectric units 1 might mutually interfere. Accordingly, in the variable type probe as shown in FIG. 1, it is difficult to constitute a convex type probe by arraying piezoelectric units 1 on a surface arcuately curved in a lengthwise direction, i.e., in a direction of array.
Therefore, an object of the present invention is to provide a variable type probe, which is easy to curvedly arrange a plurality of piezoelectric units on a curved face.
The above object of the present invention can be achieved by an ultrasonic probe including a backing member, a piezoelectric unit which is arranged on the backing member and constituted by at least three piezoelectric elements separated into one end portion, a central portion, and the other end portion, each of the piezoelectric elements having a lower face electrode thereof led out, wherein the ultrasonic probe comprises a leading-out wiring board having, on both major faces thereof, electrically conducting paths, and wherein the lower face electrode of the piezoelectric element of the one end portion being electrically led out by an upper one of the major faces of the leading-out wiring board, and the lower face electrode of the piezoelectric element of the central portion being electrically led out by a lower one of the major faces of the leading-out wiring board.
In the present invention, the leading-out wiring board having electrically conductive paths on both major faces is used, so that a lower face electrode of the piezoelectric element of the one end portion is electrically led by the upper face electric conductive path of the leading-out wiring board, and so that a lower face electrode of the piezoelectric element of the central portion is electrically led by the lower face electric conductive path of the leading-out wiring board. Therefore, the lower face electrode of the piezoelectric element of the central portion can be electrically led in a horizontal direction. Thus, according to adoption of this arrangement of the present invention, even when the surface of the backing member is arcuately curved, mutual interference among the leading-out wiring boards would not occur, so that, for example, a variable type probe formed in the convex type can be easily provided.